I agree with 4yanx's statement about getting it right by ear. Choose a method, find the VTF you like the sound of, and then continue to use the same method to check it or re-set it in the future.
Spacedeck and stylus force guage
I am setting up a Nottingham Spacedeck with Spacearm I recently bought used. The instructions with the Spacedeck say to use scales directly on the mat. The instructions with my Shure SFG-2 stylus force guage say to place it on a record. This will result in a huge differance in pressure. Which is correct?